T cell pro-inflammatory cytokine production in young adults with major depressive disorder

Background: Major Depressive Disorder (MDD) is increasingly prevalent in young adults and is a significant contributor to disease burden worldwide. Previously we have shown that young adults with MDD produce greater T cell mitochondrial ROS compared to their heathy non-depressed counterparts. Because evidence from rodent models of stress-related mood disorders demonstrates that increased T cell mitoROS drives excessive proinflammatory cytokine production, we next sought to determine if either CD4+ (Helper) or CD8+ (cytotoxic) T cells likewise produce increased proinflammatory cytokines in young adults with MDD. We hypothesized that there will be elevated proinflammatory cytokine production in young adults with MDD compared to their healthy non-depressed counterparts. Methods: Peripheral blood mononuclear cells were isolated by density centrifugation from 5 young adults with MDD having mild to moderate symptom severity and 9 non-depressed young healthy adults. Interleukin 2 (IL-2), Interleukin 6 (IL-6), Interferon Gamma (IFN-γ), and Tumor Necrosis Factor alpha (TNF-) production were assessed by flow cytometry. All data are expressed as mean SE and group differences were assessed by unpaired T test. Results: We found that adults with MDD exhibited a greater proportion of CD8+ Interleukin 6 (IL-6) (n= 8; 5 HA, 3 MDD) (HA = 22 3.5%, MDD = 255.6%; P= 0.004) producing cells compared to healthy. There were no significant differences in the proportions of CD8+ cells producing IFN-γ (HA = 14 1.2%, MDD = 3.1%; P= 0.31), IL-2 (HA =76 3.9%, MDD = 69 6.6%; P= 0.17), and TNF- (HA = 21 2.3%, MDD = 23.5%; P= 0.11) in those with MDD compared to controls. Additionally, there were no differences in CD4+ production of these same cytokines. We also assessed phenotype of the T cells using CD27 (central vs effector) and CD45 RA (Naïve vs TEMRA). Interestingly, a greater proportion of TNF- producing CD8+ and CD4+ cells exhibited an effector memory phenotype in adults with MDD compared to controls (CD8: HA = 25.8 2.4%, MDD = 46.8 3.3%; P= 0.0001; CD4+: HA=31 2.9%, MDD = 394.3%; P= 0.05). These data provide insight into the T cell subtypes that may be driving the inflammation associated with MDD. Conclusion: These preliminary findings suggest that young adults with MDD may exhibit a proinflammatory T cell phenotype characterized by greater IL-6 and TNF- production. NIH R21 MH123928 and R00133414 (JLG), NIH K01AG061271 and R01AG060395 (DWT). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.